1. Field of the Invention
The present invention relates to an apparatus for recording digital data which is applied to a digital data recorder for recording digital data on a magnetic tape by a rotary head.
2. Description of the Prior Art
As a data recorder for use in recording of measurement data, a recorder for recording such data on a magnetic tape along its longitudinal direction has been conventionally known. In case of performing the recording in the longitudinal direction, it is necessary to set the tape speed to be extremely high for attainment of high speed and high density recording. Therefore, a long time recording cannot, be made unless the tape reel is made unacceptably large. This problem does not arise in recording apparatus using a rotary head. However, in the case where the wrap angle of the magnetic tape around the guide drum lies within a range of 180.degree. to 270.degree., a discontinuous point occurs at the head switching point. In the case where the wrap angle lies within a range of 270.degree. to 360.degree., the rotary head parts from the magnetic tape, so that a discontinuous point occurs during the time when the rotary head again lands on the magnetic tape.
Therefore, it is necessary to perform the processing for this discontinuous point in order to record continuous data. In the case where the sampling frequency is distinctly determined such as an audio PCM signal, the time base compression on the basis of a predetermined ratio may be carried out. However, in the case where the sampling frequency of the input digital signal is obscure such as in a data recorder, the time base compression based on a predetermined ratio cannot be performed.
In addition, a conventional data recorder merely records and reproduces an external input and does not form a proper interface with an external computer. Therefore, it is impossible to supply a part of an input digital signal to a computer and analyze it, nor to supply graphic data from the computer to the data recorder and record it.
Thus, a method is considered whereby a buffer memory in which the recording data can be stored is provided and the data is transmitted and received between this buffer memory and the external computer. However, the data rates and data formats of the data from the computer and of the input digital signal to the data recorder do not coincide, so that if such two data and addresses are switched and written in the buffer memory, a problem will be caused since the constitution of the selector and the control for the selector become complicated.